Quality
In software terminology, quality has a very specific meaning: how suited is a given application or component to purpose - i.e. does it fulfill pre-defined or expected requirements? Furthermore, quality can refer to the level to which a given software product conforms to customers' expectations and satisfies their needs. Lastly, quality can refer to the degree to which a particular line of code fulfils requirements in terms of its inherrent points.
Cf. Wikipedia on quality.
Quality Assurance Software
This kind of software category is also called QA Tools or Quality Assurance Tools.
The term Quality Assurance (QA) refers to a way of preventing and avoiding defects and problems in products and solutions or services. E.g. ISO 9000 is a standard for defining QA.
Quality assurance is understood to mean any planned and systematic activity carried out within the system and which is set out in order to create confidence that a unit will meet the quality requirement. Quality assurance is the sum of all measures to ensure constant product quality; a distinction is made between internal and external monitoring.
In order to ensure that the software meets the requirements with regard to the various quality features (i.e. QA), there are various procedural models and methods.
Some models can be assigned to the concept of process quality. This assumes that a high-quality process of product development promotes the creation of high-quality products. Therefore, the various models make quality demands on the process in which the software is developed.
See Wikipedia for more Information on Quality Assurance.
Quality attributes/characteristics
These are the characteristics and features of a software application on which judgements of quality are based. Depending on purpose, attributes can either be spoken about in parts or as whole categories; in some usages, quality attributes may simply be referred to totem pro parte as "quality"
See Wikipedia for more information on software quality norms such as ISO/IEC 9126.
Quality control
In contrast to quality assurance (e.g. constructive and analytical QA), quality control is focussed on checking quality after development, the aim being to show that the product fulfills the requirements formulated at the beginning of the development process.
Both QA and QC are part of the quality management system (Wikipedia).